Voltage regulating apparatus



Feb. 20, 1962 3,022,458

J. G. SOLA VOLTAGE REGULATING APPARATUS Filed May 29, 1959 ff e 54 lll` IHM. III'II j -I IN V EN TOR.

fda 6642:. Ww, 47m-M M vl United States 3,22,li58 Patented Feb. 20,' 1362 3,022,453 VOLTAGE REGULATING APiARATUS Joseph G. Sola, River Forest, Ill. Filed May 29, 1959, Ser. No. 816,968 7 Claims. (Cl. 323-45) This invention relates to voltage regulating apparatus and more particularly to a voltage regulating system comprising two or more separate high reactance transformers and related capacitors for regulating voltage to a load irrespective of load variations over a certain range thereof and irrespective of line supply voltage variations over a certain range thereof, and it is an object of the invention to provide improved apparatus of this character.

It is a further object of the invention to provide improved apparatus of the character indicated for supplying a constant voltage to a load under the conditions stated.

yConstant voltage devices are lknown according to the Patent No. 2,143,745 to the same inventor as the subject application, and the present invention is an improvement thereover. Device according to the prior patent have arent Oiiice served and continue to serve satisfactorily a wide variety A of load and line supply voltage conditions. However, there recently has appeared a need for a voltage regulating and more particularly a constant voltage apparatus to supply loads requiring very high currents relative to the voltage, these loads having to be supplied with a constant or regulated voltage even though the load may vary fromno load to full load and even though the line supply voltage may vary over a rather wide range. vThe indicated need has not been completely satisfied by devices accordingto the prior patent, `and it is therefore a further object of the invention to provide'improved devices which will satisfy it.

The basic problem with which the subject inventio-n is concerned is `one of long standing. It is the problem of providing a constant or regulated voltage to a load from a particular source apparatus. There are two aspects to the problem, maintaining a constant voltage to a load when the line supply voltage varies, and maintaining a constant voltage at that load when the load current varies. The first of these aspects has been substantially solved by the Patent No. 2,143,745 already referred to, In this patent a constant voltage transformer is disclosed which utilizes a secondarywinding to which a capacitor is connected for providing a high degree of saturation in the core of the transformer associated with that winding, together with a compensating windingy which is closely coupled with the primary winding to produce a constant voltage across a load for the voltages and currents ordinarily employed. Even in circuits wherein such a constantvoltage transformer supplies a lo-adthrough a rectilier and a filter, the regulation at the load has been enabled to be achieved for the rated range of variation of primary voltages in cases wherein the output voltages were high relative to the load cur-rents required, and a certain degree of regulation has been obtained for variations in load current. In such well known apparatus the voltage drops occurring through the rectifier, iilter and the various transformer windings due to current fiow have been negligible compared to the output voltage.

However, in apparatus wherein it is desired to maintain a constant or regulated voltage across a load, for example, a D.C. load wherein the currents required are very high compared to the voltage across the load, the problem of maintaining a constant or regulated voltage across the load becomes considerably more diliicult. This is due to the fact that the resistances of the filter, the rectifier, the leads, the windings, etc., cause voltage drops due to current ow which are a much greater percentage of the outputvoltage available.

tems and apparatus of the character indicated for supplying a load, particularly a D C. load, requiring high currents relative to voltage with substantially constant volt age over rated ranges of variations in supply voltage and load current.

It is a further object of the invention to provide improved apparatus of the character indicated which are eiiicient in operation and economical of iron and copper.

Voltage regulating apparatus operating according to principles similar to those involved in this application is disclosed and claimed in application Serial No. 790,428, tiled February 2, 1959, entitled Voltage Regulating Apparatus, by the same inventor as this application.

In the apparatus as disclosed in application Serial No. 790,428, two high reactance transformers are in effect combined in a single unit, and the relatively low output voltages from each of the load transformer portions and the regulating transformer portion are obtained from windings whose turns are disposed close to the iron core. Be-

cause of the low voltages developed in these output windings, the turns thereof are few, and because of the relatively large number of amperes iiowing from these windings, the wire size is large and, consequently, is sornewhat ditlicult to use. Because of the inaccessibility of these output windings and the few turns therein, precise tap adjustments to take into account manufacturing variations and tolerances in the iron and capacitors are inconvenient and sometimes diflicult to make. Accordingly, it is a further object of the inventionto provide an improved system and apparatus of the character indicated whereinvadjustrnents, as suggested, to obtain desired outputs of voltage and current may be obtained in a more readyl and facile manner.

Further objects of the invention will become apparent as the description proceeds.

In carrying out the invention in one form, apparatus for supplying a regulated voltage to a load which may It is an object of the invention to provide improved sysbe variable over a certain range from a source of alterhating voltage, which also may be variable over a certain range, is provided comprising a load transformer having a first core, a first primary winding disposed on said first core and adapted to be supplied from `said source with an alternating voltage of predetermined nominal value and frequency, a first secondary winding disposed on said first core, a high reluctance shunt disposed between said first primary winding and said iirst secondary winding, and a first capacitor connected across said first secondary winding, asid first capacitor having a capacity value which, when taken in combination with said first secondary winding, edects under operating conditions a flux density in that portion of said iirst core associated with said iirst secondary winding substantially greater than the ilux density in that portion of said iirst core associated with said first primary winding and suiiicient to produce a condition of substantial saturation in said first secondary winding core portion, a regulating transformer having a second core, a second primary winding disposed on said second core and adapted to be supplied from said source with said alternating voltage, a second secondary winding disposed on said second core, a high reluctance shunt disposed between said second primary winding and said second secondary winding, and a secondcapacitor connected across said second secondary winding, said second capacitor having a capacity value which when taken in combination with said second secondary winding eects under operating conditions a flux density in that portion of said second core associated with said second secondary winding substantially'greater than the liux density in that portion of said second core associated with said second primary winding and sufficient to produce a condition of substantial saturation in said second secondary winding core portion, a further transformer having a primary winding and a secondary winding, a portion of said first secondary winding and a portion of said second secondary winding of lesser voltage than said portion of said rst secondary winding being connected in series with each other and to the primary winding of said further transformer, and the secondary winding of said further transformer being connectible to a load.

For a more complete understanding of the invention reference should be had to the accompanying drawing in which the only figure is a circuit diagram and schematic representation of a system and apparatus according to one embodiment of the invention.

Referring to the drawing there are shown connected in circuit relationship constant voltage type transformers 11i and 11, a substantially ordinary type transformer 12, a full wave rectifier system 13, a filter system 14, and a load 15.

The constant voltage type transformer is shown consisting of an iron core 16, a primary winding 17, a secondary winding 18, and a capacitor 19. The core 16, as shown, consists of an outer portion 21 and a central portion or leg 22, each of which is formed of individual laminations of suitable transformer steel. The outer portion 21 of the core consists of side legs 23 and 24, end legs 25 and 26 and shunt portions 27 and 28 directed inwardly, respectively, from side legs 23 and 24. The

central leg 22 includes a primary portion 29, a secondary portion 31 and shunt portions 32 and 33 directed, respectively, toward shunt portions 27 and 28 and forming therewith the non-magnetic, for example, air gaps 34 and 35.

The outer portion 21 of the transformer core is shown as consisting of continuous laminations which may be punched from a single sheet of transformer steel with the central leg 22 being pressed into appropriate recesses provided in end legs 25 and 26, the shunt portions 27 and 32 and 2S and 33 being of different lengths as shown in order that the central leg 22 may consist of punchings or laminations all oriented in the same manner as these punchings exist in the original sheet of steel. The laminations forming the central leg 22 are punched from the same piece of steel of which the laminations forming the outer leg 21 are punched, and it is desirable to replace them in the core assembly with the same orientation as the steel pieces originally occupied.

The primary and secondary windings 17 and 18 may be form-wound with the desired number of turns and disposed, respectively, on the primary and secondary core portions 29 and 31 of the central leg 22 before the central leg is pressed into the outer core portion.

The shunt portions 27 and 32 and the air gap 34 together with the shunt portions 28 and 33 and the air gap 35 form a high reluctance shunt between the primary portion of the transformer and the secondary portion whereby the fluxes generated by the primary and secondary windings 17 and 18 may link themselves to the exclusion of the other, thereby making the transformer 10 a transformer of the high reactance type.

The primary winding 17 is adapted to be connected by means of conductors 36 and 37 to a source S of suitable voltage and frequency-for example, an alternating voltage of 115 volts at 60 cycles.

A portion of the secondary winding 13 which may be ll of the winding is shown connected by means of conductors 38 and 39 to the capacitor 19, the conductor 39 being shown as terminating in a tap which can be connected to any one of the taps 41 provided on the secondary winding to enable selection of the number of turns of the secondary winding which are connected to capacitor 19 in order to adjust for variations in capacitor tolerances and transformer steel characteristics, etc. A portion it? of the secondary winding forms an output winding and is connected by means of conductors 42 and .3 to the other portions of the circuit, as will be subse= quentiy described in this specification, the conductor 43 terminatingin a tap which may be connected to any one of the taps 41 for producing a desired voltage output.

The transformer 16 together with capacitor 19 forms one separate transformer system, generally of the constant voltage type as described in Patent No. 2,143,745, whereby a substantially constant voltage may be obtained across the output portion 40 of the secondary winding 18 over a rated range of variations in voltage of the source 8.

The transformer 10 forms the load supply transformer of the system disclosed whereas the transformer 11 performs the regulation function thereof. The size of the core 16, including the thickness of the stack of laminations together with the sizes of the wire and number of turns used are selected in accordance with well-known teachings in this art.

While the core 16 has been shown as of the pressed-in type, it will be understood that other types of cores may be used, and, similarly, other constructions may be used to obtain the high leakage reactance of the primary and secondary windings.

The capacitor 19 is related to the secondary winding 18 in such a manner as to produce a very high iiux density or saturation condition in the secondary portion 31 of the central leg. In one typical form of apparatus the flux density in this portion of the core was of the order of 128,00() lines per square inch, while the liux density in the primary core portion 29 of the central leg was of the order of 102,000 lines per square inch, assuming a stacking factor of unity. The high tiux density in the secondary core portion 31 is brought about by the phenomena of ferroresonance high can occur in the apparatus as shown at appropriate voltages because the high reluctance shunts 27, 32, 34 and 28, 33, 35 enable the ux generated by the secondary winding 1S to link itself to the exclusion of the primary winding 17 By virtue of the saturation conditions existing in the secondary core portion 31, caused by the ferro-resonant phenomena, the voltage across the secondary winding 18 and, consequently, the voltage across portion 40 thereof are substantially independent of variations in the voltage across the primary winding 17.

The constant voltage type transformer 11 is shown consisting of an iron core 51, a primary winding 52, a secondary winding 53, and a capacitor 54. The core 51, as shown, consists of an outer portion 55 and a central portion or leg 56, each of which is formed of individual laminations of suitable transformer steel. The outer p0rtion 55 of the core consists of side legs 57 and 58, end legs 59 and 61 and shunt portions 62 and 63 directed inwardly, respectively, from side legs 57 and 58, The central leg 56 includes a primary portion 64, a secondary portion 65 and shunt portions 66 and 67 directed, respectively, toward shunt portions 62 and 63 and forming therewith the nonmagnetic, for example, air gaps 68 and 69.

The outer portion 55 of the transformer core is shown as consisting of continuous laminations which may be punched from a single sheet of transformer steel with the central leg S6 :being pressed into appropriate recesses provided in end legs 59 and 61, the shunt portions 62 and 66 and 63 and 67 being of different lengths as shown in order that the central leg S6 may consist of punchings or laminations all oriented in the same manner as these punchings exist in the original sheet of steel. The laminations forming the central leg 56 are punched from the same piece of steel of which the laminations forming the outer leg 55 are punched, and it is desirable to place them in the core assembly with the same orientation as the steel pieces orginally occupied.

The primary and secondary windings 52 and 53 may be form-wound with the desired number of turns and disposed, respectively, on the primary and secondary core portions 64 and 65' of the central leg 56 before the central leg is pressed into the outer core portion.

rlfhe shunt portions 62 and 66 and the air gap 68 together with the shunt portions 63 and 67 and rthe air gap 69 form a high reluctance shunt between the primary portion of the transformer and the secondary portion whereby the fluxes generated by the primary and secondary windings 52 and 53 may link themselves to the exclusion of the other, thereby making the transformer 11 a transformer of the high reactance type.

The primary winding 52 is adapted to be connected by means of conductors 70 and 79a to the same source 5.

A portion of the secondary winding 53 which may be all of the winding is shown connected by means of `conductors 71 and 72 to the capacitor 54, the conductor 71 being shown as terminating in a tap which can be connected to any one of the taps 73 provided on the secondary winding to enable selection of the number of turns of the secondary winding which are connected to capacitor 54 in order to adjust -for variations in capacitor tolerances and transformer steel characteristics, etc. A portion 80 of the secondary winding forms an output winding and is connected by means of conductors 42 and 74 to the other portions of the circuit, as will be subsequently described, the conductor 74 terminating in a tap which may be connected to any one of the taps 73 for producing a desired voltage output.

The transformer 11 together with capacitor 54 performs the regulating function according to the invention and forms one separate transformer system, generally of the constant voltage type as described in Patent No. 2,143,745, whereby a substantially constant voltage may be obtained across the output portion 80 of the secondary winding 53 over a rated range of variations in voltage of the source EGSQ,

The size of the core 51, including the thickness of the stack of laminations together withV the sizes of the Wire and number of turns used, is selected in accordance with the invention as will be described.

While the core 51 'has been shown as of the pressed-in type, it will be understood that other types of cores may be used, and, similarly, other constructions may be used to obtain the high leakage reactance of the primary and secondary windings.

The capacitor 54 is related to the secondary winding 53 in such a manner as to produce a very high flux density or saturation condition in the secondary portion 65 of the central leg. In one typical form of apparatus the ilux density in this portion of the core was of the order of 139,000 lines per square inch, while the flux density in the primary core poition 64 of the central leg was of the order of 105,000 lines per square inch, assuming a stacking factor of unity. The high ux density in the secondary portion 65 is brought about by the phenomena of ferro-resonance which can occur in the apparatus as shown at appropriate voltages because the high reluctance shunts 62, 66, 68 and 63, 67, 69 enable the iiux generated by the secondary winding S3 to link itself to the exclusion of the primary winding 50. By virtue of the saturation conditions existing in the secondary core portion 65, caused by the ferro-resonant phenomena, the voltage across the secondary Winding 53 and, consequently, the Voltage across portion 80 thereof are substantially independent of variations in the voltage across the primary winding 52.

The output voltage of the secondary winding portion 40 of the load transformer 10 is supplied to the pri mary winding 75 of transformer 12 and is opposed therein by the output voltage of the secondary winding portion S0 of the regulating transformer il; that is to say, the output voltage between conductors 42 and 74 is connected in bucking relationship to the output voltage between conductors 42 and 43 so that the vector difference of the voltages of winding portions 40 and 80 is applied to the winding 75. IIn this fashion the constant voltage vdesired at the load 15 may be obtained in the preferred core 76 upon the central leg 77 of which are disposed the primary Winding 75 and the secondary winding 78. The primary winding 75 is provided with a number of taps 79 to which the conductor 4.3 may be connected for adjustability purposes. The transformer 12 is a stepdown transformer since the invention has, as one form of application, the supply of high currents and low voltages to a load 15. Accordingly, the secondary winding '78 consists of relatively few turns and the primary winding 75 consists of a larger number of turns. The output voltage of winding portion 40 can be made large and even though diminished vectorally by the output voltage of winding portion 80, the voltage applied to the promary winding 75 may still be a substantially large voltage. This is of substantial advantage according to the invention, since it enables the transformer 12` to be disposed in close proximity to the load 15, thereby reducing the resistance drops in the connecting leads between the load and the secondary winding 78. Similarly, since the voltage between conductors 43 and 74 may be relatively large, the current flowing in these conductors to supply the desired load may be small with resultant small voltage drops, due to current flow. Thus the transformers 10 and 11 may be disposed substantial distances away, if desired, from thetransformerlZ and the load 15 without introducing objectionable additional resistance drops in the connecting leads.

The turns ratio between windings 75 and 78 can be made any value in order to lit in with the output voltage desired at the secondary winding 73 and the input voltage available from conductors 43 and 74. Since, as already pointed out, the primary winding 75 will have a large number of turns which may be of relatively small wire size, it will be a relatively simple matter to provide a sufiicient number of taps 79 in the outside layers of winding 75 to which the conductor 43 may be connected. In this manner in the final adjusting of the apparatus according to the invention, a tap 79 may be easily s'elected to give the desired voltage across the load 15 when taking into account the various manufacturing tolerances of the components and the length of the leads which are used in the installation of the apparatus. The final adjustments may, therefore, be simple and readily made, thereby effecting a lower over-all cost.

The output of secondary winding 78 is connected to a full wave rectifier 13. For this purpose, the secondary winding 78 is center tapped at 90 and a conductor 81 extends therefrom to one side of filter capacitors 82 and 83, bleeder resistor 84 and load 15. One extremity of secondary winding 78 is connected by conductor 85 to rectifier 86, conductor 87 to filter choke 88, and thence through conductor 89 to capacitor 82 and iilter choke 91, and nally through conductor 92 to capacitor 33, bleeder resistor 84 and load 15. The other extremity of secondary winding 78 is connected by means of a conductor 93 to rectifier 94 and through conductor 95 to the input of lilter 14 at the choke 88.

As thu sfar described, the transformers 16, 11 and 12, the rectifier unit 13, the iilter unit 14 and the bleeder resistor 14a provide a regulated voltage-for example, a constant voltage across the load 15, the secondary wind* ing 78, however, providing an alternating voltage to the input of full wave rectifier 13. The rectifier 13, the lter 14 and the load 15 may, of course, be considered as one D.C. load to which a regulated voltage is being supplied. Accordingly, a regulated A.C. voltage may be obtained from the output of secondary winding 78, if desired.

The load supplied by the series combination of the voltages from winding portions 4i) and Sti may be supplied with a regulated or a constant voltage irrespective of variations in current supplied to such a load and the voltage across -such load will also, according to the invention,` be independent of voltage variations in the source of supply connected to the primary windings 17 and 52 over the rated range.

A particular example of apparatus according to the disclosure thus far set forth was actually constructed and operated and provided to the load i-curreuts varying from ampere at no load to 35.5 amperes at full load, while the voltage across resistor 1.5 varied from 8.11 volts to 8.10 volts. In this same set-up, the voltage across load did not vary more than about one percent for a permissible variation in the supply voltage S from 100 volts to 130 volts. The capacitors 82 and 83, in the said practical example, each consisted of 80,000 microfarads each, and the choke coils S8 and 91 consisted of 28 turns of #6 'square copper wire. The high microfarad values of capacitors 82 and 83 provide an effective filter for any ripple components in the output voltage and in addition enable the provision of a substantially square wave input to the rectiiiers 36 and 94 whereby the rectitiers operate at high eiiiciency. Any remaining ripple components in the rectifier output voltage are effectively eliminated by the chokes 88 and 91. lt was observed in the example being described, by means of an oscilloscope, that the voltage input to the rectiiiers 86 and 94 was substantially a square wave when the load 15 was zero. However, when the load 15 was at its full value, a substantial ripple component could be observed in the Voltage input to rectiiiers 86 and 94, which ripple did not appear in any substantial magnitude in the load 15. Specifically, the ripple voltage at no load and 115 volts supply, 5, was .025 volt, peak to peak, and at full load was .090 volt.

1t is, of course, understood that in devices intended to supply low voltage and high currents to a load, such, for example, as the S volts and 35.5 ampres, approximately, which exist across and in load 15, it is necessary that the resistance drops in the circuit components be reduced to as small a value as possible. Thus, the large size wire is used for the filter chokes 88 and 91 and germanium or similar units may be used` for rectifiers 86 and 94. The voltage drop across each of the germanium rectifier units 86 and 94 was in the order of .8 of a volt per unit.

The function of the bleeder resistor 84 is to cause a continuous load current through the rectiiiers even though the current in load 15 may be zero. In this manner each rectifier is operating on the most linear portion of its characteristic. There is a drop in voltage across the rectifier units whenever there is current owing and even though it tends to be constant over a certain current range, it nevertheless increases and likewise there is an increase in voltage drop across the filter chokes 8S and 91 whenever the current therethrough increases and there are, of course, voltage drops in the various leads, the transformer windings 75 and 78 and the portions 4t) and Si) of the secondary windings. For a constant voltage to be maintained across the resistor 15 for variations in load from no load to full load, it is necessary that the transformers 10 and 11 with the various windings and capacitors provide for a voltage characteristic which will achieve this desirable end. inasmuch as an increase in current causes an increase in voltage drop throughout these components as described, it is necessary that the secondary winding portions 4t) and 80 together provide a rising voltage with increasing load currents.

In the actual example being described, the voltage across winding portion Si) at no load was 455 volts when the primary winding 17 was connected to a source of supply S of 115 volts at 60 cycles. At a full load of 35.5 amperes D C. in load 15, the voltage across this same winding was 441 volts. Yet, under similar conditions at no load, the voltage in regulating winding 80 was 165.5 volts and at full load this voltage was 173 volts. And in the said particular device, even through the voltage Vof the winding portions '40 and 80 were connected in bucking relationship in the circuit .supplying the .transformer 12 and thus ultimately the load 15, the voltage across the primary winding 75 at no load was 290 volts and at full load was 360 volts, or an increase of about 23 percent. The corresponding voltages for the full winding 78 under the same conditions were 17.60 and 21.10. This increase in voltage appearing in the secondary winding 7S compensated for the voltage drops through the rectifiers, the filter and leads, etc., so that the voltage across load 15 at no load was 8.11 volts and at full load was 8.10 volts.

ln the said particular example, the transformer 10 has been designated as the load supplying transformer and the transformer 11 has been designated as the regulating transformer, and the constructional features thereof may now be given for a fuller understanding of the invention.

The primary winding 17 consisted of 120 turns of #14 copper' wire, the secondary winding 18 consisted of 490 turns of #15 copper wire, the number of turns in portion 49 of winding 1S being 3751/2. The capacitor 19 was 10 microfarads. The core 16 consisted of a 21,356" stack of transformer steel laminations, 26 gauge cold reduced, designated as lvl-22 by the manufacturer thereof. The exterior dimension of the core along the sides 23 and 24 was 5%, and the length along the ends 25 and 26 was also 5%". The width of the lcentral leg 22 was 11/4" whereas the width of the outside legs 23 and 24 and the width of the cnd legs 25 and 26 was 7As. The shunt members 27, 32 and 28, 33 were of the same height as the thickness of the stack and each had a width of S/s". The length of the shunt members 27 and 32 and 28 and 33 was such as to provide air gaps 34 and 35 of .040.

The primary winding 52 consisted of 240 turns of #16 copper wire, the secondary winding 53 consisted of 1040 turns of #18 copper wire, the number of turns in portion Si? of winding 53 being 280. The capacitor 54 was 5 microfarads. The core 51 consisted of a 1% stack of transformer steel laminations, 26 gauge cold reduced, designated as M22, by the manufacturer thereof. The dimensions of the core 51 including the outer legs, the central leg, the shunts and the air gap Wcre the same as those of core 16.

The transformer 12 as has been indicated was of an ordinary close coupled type in which the central leg had a width of ls/s", the stack height being 1%, the primary winding 75 having 495 turns of #19 copper wire with taps thereon and the secondary Winding 78 having a total of 15 turns of #6 double copper wire, this winding being center tapped.

The tilter chokes S8 and 91, each consisted of a core having a 13/3 stack of 24 gauge laminations and two .013" non-magnetic gaps.

With the various constants of the apparatus given, it was found that under no-load conditions, there is no current flowing in load 15 but with 110 volts at 60 cycles supplied to the primary windings 17 and 52, the voltage across capacitor 19 was 598 volts which dropped to 589 volts at full load. Under these same conditions, the voltage across capacitor 54 was 640 volts at no load and this increased to 660 volts at full load.

As has been indicated, the rated range of primary voltage variation or' the device made and tested was from to 13G volts. At 100 volts across the primary windings 17 and 51., at no load, the voltage existing across the load 15 was 8.16 volts and at full load was 8.02 volts or a decrease of 1.7 percent; at 130 volts across the primary windings, the voltage across the load 15 was 8.08 volts at no load, and 8.12 volts at full load, or a decrease of about .5 percent. Thus, it is seen that the example described has a maximum regulation of about 1.7 percent at one extreme of permissible range of primary volt- .age variation and regulation of .5 percent at the other extreme of the permissible range of primary voltage variation. For the nominal value of volts, the voltage across load 15' changes from 8.11 to 8.10 from no load to full load; that is to say, there was virtually no change.

One characteristic of the device, as has already been described, is that the voltage across the conductors 42 and '74 increased, the voltage across the conductors 42 and 43 decreased with increasing load current, yet the resultant voltage of the secondary winding portions 4h and 80, connected in bucking relationship, rises a sufficient amount to compensate for the voltage drops through the rectifier, filter circuit, leads, etc.

This phenomena is believed explainable on the basis of shifts in the voltage vectors for portions 40 and Sil of the secondary windings 18 and S3, respectively. The phase shifts in these two voltages is enabled to take place because of the reactance which exists in these secondary windings as determined by the inductive reactance of the windings and the capacitive reactance of the capacitors connected thereto and by the fact that the load supplied by the transformers is a resistance which provides a resistive component of voltage which exists vectorally in the circuit. The voltage measurement and observation of the apparatus in operation indicates that the voltage vector of secondary winding portion 40 tends to shift substantially relatively to the primary winding voltage whereas the voittage vector of the secondary winding portion 80 tends to remain fixed relative to the primary voltage vector.k

It was also observed that power was actually supplied to the transformer 11 from the transformer 11i-during at least some portions of the no-load to full-load operation. The transformer 11 was evidently acting purely as a voltage regulating transformer and not as a load supplying transformer. The voltage of winding portion 40 was, of course, smaller than the voltage existing across the secondary Winding portion 80 `and thus current was forced to fiow against the voltage of the secondary winding portion 80. This can explain the voltage rise existing in the secondary winding 53 and in the portion 80' which are also expl-ainable on the basis that leading `current is flowing through an inductive circuit. Thus it has been found that the voi-tage of winding portion 80 which is opposed to the voltage of winding portion 40 should be less than the latter voltage. It has also been found that the size or rating of the regulating transformer may vary from a size equal to that of the load transformer to a size substantially less, for example half size or less, and still produce the desired regulatinng function.

A balance must be achieved between the various components of the circuit-namely, the number of turns in the windings, the dimensions of the air gaps, the microfarad values of the capacitors, and the dimensions of the iron core to achieve a desired result, and variations may be selected in each of the components indicated to fit different conditions.

While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto since many modifications may be made, and it is, therefore, contemplated by the appended claims to cover any such modifications as fall Within the true spirit andpscope of the invention.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

l. Apparatus for supplying a regulated voltage to a load which may be variable over a certain range from a source of alternating voltage which also may be variable over a certain range comprising a load transformer having a rst core, a first primary Winding disposed on said first core and adapted to be supplied from said source with an alternating voltage of predetermined nominal value and frequency, a first secondary winding disposed on said first core, a high reluctance shunt disposed between said first primary winding and said first secondary winding, and a capacitor connected across said first secondary winding, sai-d capacitor having ya capacity value which when taken in combination with said first secondary winding eects under operating conditions a flux density in the portion of said first core associated with said first secondary winding substantially greater than the flux density in that por- 10 tion of said first core associated with said rst primary winding and sufficient to produce a condition of substantial saturation in said first. secondary winding core portion, a regulating transformer having a second core, a second primary winding disposed on said second core and adapted to be supplied from said source with said alternating voltage, a second seconda-ry winding disposed on said second core, a high reluctance shunt disposed between said second primary winding and said second secondary winding, and a capacitor connected across said second secondary winding, said capacitor having a capacity value which when taken in combination with said second secondary winding effects under operating conditions a flux density in that portion of said second core associated with said second secondary winding substantially greater than the fiux density in that portion of said second core associated with said second primary winding and suiiicient to produce `a condition of substantial satura.- tion in said second secondary winding core portion, a further transformer having a primary winding and a secondary winding, a portion of said first secondary winding and a portion of said second secondary winding of lesser voltage than said portion of said first secondary winding being connected in series with each other and to the primary winding of said further transformer, and the secondary winding of said further transformer being connectible to a loa-d.

2. Apparatus for supplying a regulated voltage to a load which may be variable over a certain range from a source of alternating voltage which also may be variable over a certain range comprising a load transformer having `a first core, a first primary winding disposed on said first core `and adapted to be supplied from said source with an alternating voltage of predetermined nominal value and frequency, a first secondary winding disposed on said first core, a high reluctance shunt disposed between said first primary winding and said first secondary winding, and a capacitor connected across said first secondary winding, said capacitor having a capacity value which when taken in combination with said first secondary winding effects under operating conditions a flux density in that portion of said first core associated with said first secondary winding substantially greater than the fiux density in that p0rtion of said first core `associated with said first primary winding and sufficient to produce a condition of substantial saturation in said first secondary winding core portion, a regulating transformer having a core, a second primary winding disposed on said second core and adapted to be supplied from said source with said alternating voltage, a second secondary winding disposed on said second core, a high reluctance shunt disposed between said second primary winding and said second secondary winding, and a capacitor connected across said second secondary winding, said capacitor having a capacity valne which when taken in combination with said second secondary winding effects under operating conditions a iiux density in that portion of said second core associated with said second secondary winding substantially greater than the flux density in that portion of said second core associated with said second primary winding and sufficient to produce a condition of substantial saturation in said second secondary winding core portion, a further transformer having a primary winding and a secondary winding, a portion of said first secondary winding and a portion of said second secondary winding of lesser voltage than said portion of said first secondary winding being connected in series bucking relationship with each other and to the primary winding of said further transformer, and the secondary winding of said further transformer being connectible to a load.

3. Apparatus for supplying a regulated voltage to a load which may be variable over a certain range from a source of alternating voltage which also may be variable over a certain range comprising a load transformer having a first core, a first primary winding disposed on said spaanse first 'core and adapted to be supplied from said source with an alternating Voltage of predetermined nominal value and frequency, a first secondary winding disposed on said first core, a high reluctance shunt disposed between said first primary winding and said first secondary winding, and a capacitor connected across said first secondary winding, said capacitor having a capacity value which when taken in combination with said first secondary winding effects under operating conditions a fiux density in that portion of said first core associated with said secondary Winding substantially greater than the flux density in that portion of said first core associated with said first primary winding and sufficient to produce a condition of substantial saturation in said first secondary winding core portion, a regulating transformer having a second core, a second primary winding disposed on said second core and adapted to be supplied from said source with said alternating voltage, a second secondary winding disposed on said second core, a high reluctance shunt disposed between said second primary winding Vand said second secondary winding, and a capacitor connected across said second secondary winding, said capacitor having a capacity value which when taken in combination with said second secondary winding effects under operating conditions a flux density in that portion of said second core associated with said secondary winding substantially greater than the uX density in that portion of said second core associated with said second primary winding and sufhcient to produce a condition of substantial saturation in said second secondary winding core portion, a further transformer having a primary winding and a secondary winding, a portion of said first secondary winding and a portion of said second secondary winding of lesser voltage than said portion of said first secondary winding being connected in series bucking relationship with each other and to the primary winding of said further transformer, the secondary winding of said further transformer being connectible to a load, and means for causing a resistive component of current to flow in the series circuit of said first and second secondary windings portions under operating conditions whereby to effect a relative phase change in the voltages across said winding portions.

4. Apparatus for supplying a regulated voltage to a 4load which may be variable over a certain range from a source of alternating voltage which also may be variable over a certain range comprising a load transformer having a first core, a first primary winding disposed on said rst core and adapted to be supplied from said source with an alternating voltage of predetermined nominal value and frequency, a first secondary winding disposed on Vsaid first core, a high reluctance shunt disposed between said first primary winding and said first secondary winding, and a capacitor connected across said first secondary winding, said capacitor having a capacity value which when taken in combination with said first secondary Winding effects under operating conditions a flux density in that portion of said first core associated with said secondary winding substantially greater than the flux density in that portion of said first core associated with said rst primary winding and sufficient to produce ka condition of substantial saturation in said first secondary winding core portion, a regulatng transformer having a second core, a second primary winding disposed on said second core and adapted to be supplied from said source with said alternating voltage, a second secondary winding disposed on said second core, a high reluctance shunt disposed between said second primary winding and said second secondary winding, and a capacitor connected across said second secondary winding, said capacitor having a capacity vaiue which when taken in combination with said second secondary winding effects under operating conditions a dux density secondary winding substantially greater than the iux density in that portion of said second core associated with said second primary winding and sufficient to produce a condition of substantial saturation in said second secondary winding core portion, a further transformer having input terminals and output terminals, means for deriving one voltage from said first secondary winding, means for deriving a voltage of less magnitude than said one voltage from said second secondary winding, said means being connected in series with each other with the derived voltages in bucking relationship and being connected to the input terminals of said further transformer, the output terminals of said further transformer being connectible to a load, and means for causing a resistive component of current to flow in the series circuit of said voltage deriving means portions under operating conditions whereby to effect a relative phase change in the voltages across each of said voltage deriving means.

5. Apparatus for supplying a regulated voltage to a load which maybe variable over a certain range from a source of alternating voltage which also may be variable over a certain range comprising a load transformer having a first core, a'first vprimary winding disposed on said first core and adapted to be supplied from said source with an alternating voltage of predetermined nominal value and frequency, a first secondary winding disposed on said first core, a high reluctance shunt disposed between said first primary winding and said first secondary winding, and a 'capacitor connected across said first secondary winding, said capacitor having a capacity value which when taken in combination with said first secondary winding effects under operating conditions a fiux density in that portion of said rst core associated with said secondary winding substantially greater than the fiux density in that portion of said first core associated with said first primary winding and sufficient to produce a condition of substantial saturation in said first secondary Winding core portion, a regulating transformer having a second core, a second primary winding disposed on said second core and adapted to be supplied from said source with said alternating voltage, a second secondary winding disposed on said second core, a high reluctance shunt disposed between said second primary -winding and said second secondary winding, a further transformer having a primary winding and a second winding, a portion of said first secondary winding and a portion of said second secondary Winding of lesser voltage than said portion of said first secondary winding being connected in series bucking relationship with each other and to the primary winding of said further transformer, the secondary Winding of said further transformer being connectible to a load, and means for causing a resistive component of current to flow in the series circuit of said first and second secondary winding portions whereby to effect a relative phase change in the voltages across said winding portions.

6. Apparatus for supplying a regulated voltage to a load which may be variable over a certain range from a source of alternating voltage which also may be variable over a certain range comprising a load transformer having a first core, a first primary winding disposed on said first core and adapted to be supplied from said source with an alternating voltage of predetermined nominal value and frequency, a first secondary winding disposed on said first core, a high reluctance shunt disposed between said rst primary winding and said first secondary winding, and a capacitor connected across said first secondary winding, said capacitor having a capacity value which when taken in combination with said first secondary winding effects under operating conditions a flux density in that portion of said first core associated with said secondary winding substantially greater than the iiux density in that portion of said first core associated with said first primary winding and sufficient to produce a condition of substantial saturation in said first secondary winding core portion, a regulating transformer having a second core, a second primary winding disposed on said second core and adapted to be supplied from said source with said alternating voltage, a second secondary winding disposed on said second core, a high reluctance shunt disposed between said second primary winding and said second secondary winding, and a capacitor connected across said second secondary winding, said capacitor having a capacity value which when taken in combination with said second secondary winding effects under operating conditions a flux density in that portion of said second core associated with said secondary winding substantially greater than the flux density would be in'that-portion in the absence of said capacitor, a further transformer having a primary winding and a secondary winding, a portion of said first secondary winding and a portion of said second secondary winding of lesser voltage than said portion of said first secondary -winding being connected in series bucking relationship with each other and to the primary winding of said further transformer, the secondary winding of said further transformer being connectible to a load, and means for causing a resistive component of current to liow in the series circuit of said tirst and second secondary winding portions under operating conditions whereby to effect a relative phase change in the voltages across said winding portions.

7. Apparatus for supplying a regulated Voltage to a load which may be variable over a certain range from a source of alternating voltage which also may be variable over a certain range comprising a load transformer having a first core including a first central leg and two outer legs, a first primary winding disposed on said first central leg and adapted to be supplied from said source with an alternating voltage of predetermined nominal value and frequency, a first secondary winding disposed on said first central leg, a high reluctance shunt disposed between said first primary winding and said first secondary winding, and a capacitor connected across said first secondary winding, said capacitor having a capacity value which when taken in combination with said first secondary winding effects under operating conditions a flux density in that portion of said first core associated with said secondary winding substantially greater than the fiuX density in that portion of said first core associated with said first primary winding and suicient to produce a condition of substantial saturation in said rst secondary winding core portion, a regulating transformer having a second core including a second central leg and two outer legs, a second primary winding disposed on said second `central leg and adapted to be supplied from said source with said alternating voltage, a second secondary winding disposed on said second central leg, a high reluctance shunt disposed between said second primary winding and said second secondary winding, and a capacitor connected across said second secondary winding, said capacitor having a capacity value which when taken in combination with said second secondary winding effects under operating conditions a flux density in that portion of said second core associated with said secondary Winding substantially greater than the flux density in that portion of said second core associated with said second primary winding and sufficient to produce a condition of substantial saturation in said second secondary winding core portion; a further transformer having a primary winding and a secondary winding, a portion of said first secondary winding and a portion of said second secondary Winding of lesser voltage than said portion of said first secondary winding being connected in series bucking relationship with each other and to the primary winding of said further transformer, the secondary winding of said further transformer being connectible to a load, and means for causing a resistive component of current to flow in the series circuit of said first and second secondary winding portions whereby to effect a relative phase change in the voltages across said winding portions.

References Cited in the file of this patent UNITED STATES PATENTS 

